Thanks for that, my sharp shooting friend.
I don't know if you have any branches of the £uków chain of butchers' shops in Kraków, but they take orders for offal.
I will have a look about and see if I can find it :)
Also Kuchnie Świata in Warsaw often have haggis, albeit tinned.
I am sure if that is the case then they will have some in the Kraków branch too. I fancy making it as it will be a good bit of fun, but this is a good idea as a last resort.